Using the reductive perturbation method,a Korteweg-de Vries (KdV) equation is derived to study the nonlinear properties of electrostatic collisionless dust acoustic solitons in pair-ion-electron (p-i-e) plasmas.The Buid model is chosen for positive ions,negative ions,and the fraction of electrons and charged (both positive and negative)dynamic dust particles.It is realized that electrostatic hump structures can be found when the dust particles are positively charged,and electrostatic dip structures can be detected for negatively charged dust particles.Numerical solutions for these dust acoustic solitous are plotted and their characteristics are discussed.It is found that the amplitude and width of the electrostatic dust acoustic solitons increase when the density of the dust particles and/or the temperature of the negative ions increases,and that the amplitude and width of these solitons decrease when the temperature of the positive ions increases.As pair-ion plasmas mimic electron-positron plasmas,our results might be helpful in understanding the nonlinear dust acoustic solitary waves in super dense astronomical bodies like neutron stars.